Did you ever get this situated? I’m having the same issue. Brakes only work the last 3rd of the pedal. If I clamp down on one of the front brake hoses, the pedal pressure is much higher! And I put the old return springs on after I fitted new pads.... so frustrating!
Have you gotten all the air out of the front brakes?
I'd suggest removing the drum on the offending wheel and, using levers between the hub flange and the brake shoes, try levering the shoes outwards a little. The brake shoes should remain where they are moved to, if the adjusters are holding correctly. If the shoes slip inwards, the adjusters aren't working properly.
The usual cause of this is, as you've already discovered, is the return springs are either too strong or too short.(= same result). Some here recommend stretching new springs so that they are approx. 6mm longer than they were, others recommend just re-fitting the original springs. There also seems to be some difference in 'gripping power' between the 3? different styles of brake shoe adjuster used at different times. Some of these adjusters can be dismantled.
I've tried various dodges to get the adjusters to grip more effectively.....
Things I tried :-
1) Increased the spring force in the adjuster
2) Cleaned off any paint on the brake shoe in the region of the adjuster
3) Ditto, but caused the brake shoe to rust where the adjuster fits (Baker's Soldering Fluid or Phosphoric? Acid will cause steel to rust rapidly)to improve grip
4) Tried dimpling the brake shoe in the region of the adjuster using a centre (dot) punch to try to improve grip
5) Tried putting grooves on the brake shoe in the region of the adjuster using a cold chisel to try to improve grip
6) Tried sanding the hard friction on the adjusters to improve grip
7) Tried replacing the hard friction washers on the adjusters with regular fibre washers.
Best and easiest solution was to simply source and fit softer (less powerful) return springs so that the brake shoe adjusters could do their job and not be overwhelmed by return springs that are too strong.
Be careful that no lubricant gets between the brake adjuster and the brake shoe - or they'll never grip/work.
Al.